U.S. patent number 6,321,092 [Application Number 09/396,235] was granted by the patent office on 2001-11-20 for multiple input data management for wireless location-based applications.
This patent grant is currently assigned to Signal Soft Corporation. Invention is credited to James Fitch, David L. Hose, Michael McKnight.
United States Patent |
6,321,092 |
Fitch , et al. |
November 20, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Multiple input data management for wireless location-based
applications
Abstract
Multiple location finding equipment (LFE) inputs are used to
enhance the location information made available to wireless
location-based applications. In one implementation, the invention
is implemented in a wireless network including an MSC (112) for use
in routing communications to or from wireless stations (102), a
network platform (114) associated with the MSC (112), and a variety
of LFE systems (104, 106, 108 and 110). A Location Finding System
(LFS) (116) in accordance with the present invention is resident on
the platform (114). The LFS (116) receives location information
from the LFEs (104, 106, 108 and 110) and provides location
information to wireless location based applications (118). In this
regard, the LFS (116) can receive input information at varying time
intervals of varying accuracies and in various formats, and can
provide standardized outputs to the applications (118), for
example, depending on the needs of the applications (118). Multiple
inputs may also be co-processed for enhanced accuracy.
Inventors: |
Fitch; James (Edmonds, WA),
Hose; David L. (Boulder, CO), McKnight; Michael
(Westminster, CO) |
Assignee: |
Signal Soft Corporation
(Boulder, CO)
|
Family
ID: |
26804055 |
Appl.
No.: |
09/396,235 |
Filed: |
September 15, 1999 |
Current U.S.
Class: |
455/456.5 |
Current CPC
Class: |
H04W
8/08 (20130101); G01S 5/12 (20130101); H04W
64/00 (20130101); H04W 4/029 (20180201); G01S
5/02 (20130101); G01S 5/0027 (20130101); H04W
4/02 (20130101); H04W 88/18 (20130101) |
Current International
Class: |
G01S
5/12 (20060101); H04Q 7/38 (20060101); G01S
5/00 (20060101); G01S 5/02 (20060101); H04Q
007/20 () |
Field of
Search: |
;455/456,422,457,517
;342/357,450,457 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
WO 98/10307 |
|
Mar 1998 |
|
WO |
|
WO 98/10538 |
|
Mar 1998 |
|
WO |
|
Primary Examiner: Maung; Nay
Assistant Examiner: Vuong; Quochien B.
Attorney, Agent or Firm: Marsh Fischmann & Breyfogle
LLP
Parent Case Text
This applications claims benefit of Prov. No. 60/106,816 filed Nov.
3, 1998.
Claims
What is claimed is:
1. A method for use in a wireless network to obtain requested
location information regarding a wireless station from any of
various location sources and provide the requested location
information to a wireless location application, the wireless
network being associated with at least a first source of location
information and a second source of location information for
providing information regarding locations of wireless stations in
the network, the method comprising the steps of:
first receiving a location request regarding said wireless station
from said wireless location application, said location request
seeking said requested location information;
second receiving a first location input based on first location
information from said first source, and a second location input
based on second location information provided by said second
source, wherein said first location information and said second
location information are provided in different formats relating to
identification of wireless station locations;
wherein said first location finding equipment employs a first
location finding technology and said second location finding
equipment employs a second location finding technology different
than said first location finding technology, and said step of
second receiving comprises standardizing information obtained from
said first location finding equipment and second location finding
equipment to provide said respective first and second location
inputs, wherein said first and second location inputs include
location information in a standardized format;
storing data in memory relating to said first location input and
said second location input;
obtaining said requested location information by selectively
retrieving data from said memory based on said location request;
and
outputting said requested location information to said wireless
location application, wherein said wireless location application is
supported by said first location finding equipment and said second
location finding equipment, wherein said step of first receiving
comprises providing an interface defining a format for receiving a
location request from said wireless location application, said
format allowing said wireless location application to specify at
least one parameter regarding said request location information,
and receiving said location request in accordance with the defined
format.
2. A method as set forth in claim 1, wherein said step of second
receiving comprises providing a first location finding controller
associated with said first source for receiving data from said
first source in a first data format, providing a second location
finding controller associated with said second source for receiving
second data from said second source in a second format, and
operating said first and second location finding controllers to
convert said respective first and second data into standardized
location data.
3. A method as set forth in claim 1, wherein said step of storing
comprises storing information for individual wireless stations
including at least a location and a time.
4. A method as set forth in claim 1, wherein said step of storing
comprises storing information for individual wireless stations
including an uncertainty regarding location.
5. A method as set forth in claim 1, wherein said step of storing
comprises information for individual wireless stations including
one of a travel speed and a travel direction.
6. A method as set forth in claim 1, wherein said step of first
receiving comprises obtaining information regarding the identity of
a wireless station and a specification concerning the requested
location information.
7. A method as set forth in claim 1, wherein said step of obtaining
comprises identifying said parameter of the location request
regarding the desired location information and determining whether
the stored data includes information conforming to the
parameter.
8. A method as set forth in claim 1, wherein said step of obtaining
comprises prompting one of the first source and the second source
to obtain location information regarding the wireless station in
response to the location request.
9. A method as set forth in claim 1, wherein said step of
outputting comprises providing an output including at least a
wireless station identification and a location of the wireless
station.
10. A method as set forth in claim 1, wherein said step of
outputting comprises providing an output including a time and an
uncertainty regarding location.
11. A method as set forth in claim 1, wherein said step of
outputting comprises providing an output including one of a speed
of travel and direction of travel for the wireless station.
12. A method as set forth in claim 1, further comprising combining
multiple location finding equipment inputs for the wireless station
to make a location determination.
13. A method as set forth in claim 12, wherein said step of
combining comprises obtaining a first set of information including
first location information and first time information for said
wireless station, obtaining a second set of information including
second location information and second time information for said
wireless station, determining a time difference between said first
and second sets of information, and adjusting one of said first and
second sets of information based on said time difference.
14. A method as set forth in claim 13, wherein said adjusting
comprising calculating one of a change in position and an
uncertainty in position based on said time difference.
15. A method as set forth in claim 12, wherein said step of
combining comprises obtaining a first set of position information
including a position and an uncertainty, obtaining a second set of
information including a position and an uncertainty and combining
said first set and said second set to yield a third set including a
position and an uncertainty for said wireless station, wherein said
third set includes a reduced uncertainty relative to said first and
second sets.
16. A method as set forth in claim 12, wherein said first location
finding technology involves a first location finding controller for
receiving first raw location data from said first source and
aggregating said first raw data to provide said first location
input and said second location finding technology involves a second
location finding controller for receiving second raw location data
from said second source and aggregating said second raw data to
provide said second location input, and said step of combining
comprises obtaining said first raw data from said first source,
obtaining said second raw data from said second source, and said
step of combining further comprises using one of said first raw
data and said second raw data to obtain derived location
information.
17. A method as set forth in claim 1, further comprising the step
of obtaining tracking information regarding movement of said
wireless station, and using said tracking information to derive
location information.
18. A method as set forth in claim 17, wherein said step of
deriving tracking information comprises receiving first location
information obtained for a first time and obtaining second location
information obtained for a second time and deriving said tracking
information based on said first and second location information
wherein said tracking information comprises at least one of speed
of travel information and direction of travel information.
19. A method for use in a wireless network to obtain requested
location information regarding a wireless station from any of
various location sources and provide the requested location
information to a wireless location application, the wireless
network being associated with at least a first source of location
information and a second source of location information for
providing information regarding locations of wireless stations in
the network, the method comprising the steps of:
receiving a first location input based on first location
information from said first source and a second location input
based on second location information provided by said second source
wherein, said first location information and said second location
information are provided in different formats relating to
identification of wireless station locations;
combining said first location input from said first location
finding equipment and said second location input from said second
location finding equipment; and
outputting said requested location information to said wireless
location application based on said step of combining said first
location input and said second location input, wherein said first
location finding equipment employs a first location finding
technology and said second location finding equipment employs a
second location finding technology different than said first
location finding technology, said first location finding technology
involves a first location finding technology, said first location
finding technology involves a first location finding controller for
receiving first raw location data from said first location finding
equipment and aggregating said first raw data to provide said first
location input and said second location finding technology involves
a second location finding controller for receiving second raw
location data information from said second location finding
equipment and aggregating said second raw data to provide said
second location input, and said step of combining comprises
obtaining said first raw data from said first location finding
equipment, obtaining said second raw data from said first location
finding equipment, obtaining said second raw data from said second
location finding equipment, and said step of combining comprises
using one of said first raw data and said second raw data to obtain
derived location information.
20. A method for use in a wireless network to obtain requested
location information regarding a wireless station and provide the
requested location information to a wireless location application,
the wireless network being associated with location finding
equipment for providing information regarding locations of wireless
stations in a network service area, the method comprising the steps
of:
receiving a plurality of device dependent location inputs provided
by said location finding equipment, each of said device dependent
inputs having one of a data structure and a data content dependent
on a type of the location finding equipment;
receiving a device independent location request from said wireless
location application, the device independent location request being
in accordance with a standard protocol defining requested location
information independent of any particular type of location finding
equipment,
storing data in memory based on said plurality of device dependent
location inputs;
obtaining said requested location information by performing a query
of said data based on said device dependent location inputs and
selectively retrieving data from said memory based on said device
independent location request; and
outputting said requested device independent location information
to said wireless location application, wherein wireless location
equipment independent information is provided to wireless location
applications based on wireless location equipment dependent inputs
such that said application can operate free from restriction to a
particular type of the location finding equipment.
Description
FIELD OF THE INVENTION
The present invention relates in general to wireless location-based
applications and, in particular, to a method and apparatus for use
in processing multiple location finding equipment inputs and making
the resulting location information available to wireless
location-based applications.
BACKGROUND OF THE INVENTION
Wireless communications networks generally allow for voice and/or
data communication between wireless stations, e.g., wireless
telephones (analog, digital cellular and PCS), pagers or data
terminals that communicate using RF signals. In recent years, a
number of location-based service systems have been implemented or
proposed for wireless networks. Such systems generally involve
determining location information for a wireless station and
processing the location information to provide an output desired
for a particular application.
Examples of such existing or proposed applications include
emergency or "911" applications, location dependent call billing,
cell-to-cell handoff and vehicle tracking. In 911 applications, the
location of a wireless station is determined when the station is
used to place an emergency call. The location is then transmitted
to a local emergency dispatcher to assist in responding to the
call. In typical location dependent call billing applications, the
location of a wireless station is determined, for example, upon
placing or receiving a call. This location is then transmitted to a
billing system that determines an appropriate billing value based
on the location of the wireless station. In handoff applications,
wireless location is determined in order to coordinate handoff of
call handling between network cells. Vehicle tracking applications
are used, for example, to track the location of stolen vehicles. In
this regard, the location of a car phone or the like in a stolen
vehicle can be transmitted to the appropriate authorities to assist
in recovering the vehicle.
From the foregoing, it will be appreciated that location-based
service systems involve location finding equipment (LFE) and
location-related applications. To some extent, the LFEs and
applications have developed independently. In this regard, a number
of types of LFEs exist and/or are in development. These include
so-called angle of arrival (AOA) time difference of arrival (TDOA),
handset global positioning system (GPS) and the use of cell/sector
location. The types of equipment employed and the nature of the
information received from such equipment vary in a number of ways.
First, some of these equipment types, like GPS, are wireless
station-based whereas others are "ground-based", usually
infrastructure-based. Some can determine a wireless station's
location at any time via a polling process, some require that the
station be transmitting on the reverse traffic channel (voice
channel), and others can only determine location at call
origination, termination, and perhaps registration. Moreover, the
accuracy with which location can be determined varies significantly
from case to case. Accordingly, the outputs from the various LFE's
vary in a number of ways including data format, accuracy and
timeliness.
The nature of the information desired for particular applications
also varies. For example, for certain applications such as 911,
accuracy and timeliness are important. For the applications such as
vehicle tracking, continuous or frequent monitoring independent of
call placement is a significant consideration. For other
applications, such as call billing, location determination at call
initiation and call termination or during handoff is generally
sufficient.
Heretofore, developers have generally attempted to match available
LFEs to particular applications in order to obtain the location
information required by the application. This has not always
resulted in the best use of available LFE resources for particular
applications. Moreover, applications designed to work with a
particular LFE can be disabled when information from that LFE is
unavailable, e.g., due to limited coverage areas, malfunctions or
local conditions interfering with a particular LFE modality. In
addition, the conventional query and response mode of operation
between applications and the associated LFEs has resulted in the
use by applications of LFE dependent data formats, LFE limited data
contents, and single LFE input location determinations.
SUMMARY OF THE INVENTION
The present invention is directed to a method and apparatus for
using multiple LFE inputs to enhance the location information made
available to wireless location-based applications. The invention
allows wireless location-based applications access to information
based inputs from LFEs of different types, thereby enhancing the
timeliness, accuracy and/or reliability of the requested location
information. Moreover, in accordance with the present invention,
applications are independent of particular LFEs and can access
location information from various LFE sources without requiring
specific adaptations, data formats, or indeed knowledge of the LFE
sources employed, in order to access and use such location
information. By virtue of such independence, new location finding
technologies can be readily deployed and existing applications can
exploit such new technologies without compatibility issues. The
invention also allows multiple LFE inputs, from one or more LFEs,
to be used to allow for wireless station tracking and reduced
location uncertainty.
According to one aspect of the present invention, a method is
provided for using multiple (i.e., two or more) LFEs to support a
wireless location application. The method involves receiving first
and second inputs from first and second LFEs, storing location
information based on the inputs in memory, receiving a location
request regarding a wireless station from a wireless location
application, selectively retrieving the location information from
memory, and outputting a response to the location request to
wireless location application.
The first and second LFEs preferably may employ different location
finding technologies, e.g, GPS, AOA, TDOA, and cell/sector
technologies. The stored location information preferably includes
at least location information and corresponding time information
for particular wireless stations, and may further include location
uncertainty information, travel speed information and travel
direction information. In response to the location request from the
wireless location application, location information may be
retrieved from memory or, alternatively, one or more of the LFEs
may be prompted to obtain location information. In this regard, the
location request may include a specification regarding the desired
location information, for example, indicating how recent or how
accurate the information should be. If the memory includes
information conforming to the specification, then such information
is retrieved and output to the requesting application. Otherwise,
appropriate information may be obtained by prompting one or more
LFEs to locate the wireless station of interest.
In accordance with another aspect of the present invention, a
processing system is interposed between the LFEs and the wireless
location applications such that the applications can access
location information in a manner that is independent of the
location finding technology employed by the LFEs. The corresponding
process implemented by the processing system involves: receiving
LFE dependent location data (i.e., location data having a content
and/or format dependent on the location finding technology
employed) from multiple LFEs receiving a location request from a
wireless location application seeking LFE independent location data
(i.e., location data having a content and format independent of any
particular location finding technology) and responding to the
location request based on LFE dependent location data. The process
implemented by the processing system may further involve generating
and storing LFE independent location data based on the LFE
dependent data. The processing system may be resident on the
location finding controllers associated with each LFE, on a
separate platform and/or the processing system functionality may be
distributed over multiple platforms.
According to a still further aspect of the present invention,
multiple LFE inputs, are utilized to make a location determination
regarding a wireless station. The corresponding method involves the
steps of receiving a first location input from a first LFE
including first location information and first uncertainty
information, receiving a second location input from a second LFE
including second location information and second uncertainty
information and combining the first and second location inputs to
provide a combined location input including combined location
information and uncertainty information based on the first and
second inputs. Preferably, the first and second inputs include raw
location and uncertainty information obtained from LFE measurements
prior to aggregation and related processing. One or both of the
first and second inputs may constitute partial information,
insufficient on its own to yield a location and uncertainty
regarding the wireless station within the requirements of the
wireless location application. For example, in the case of LFEs
that determine location based on readings obtained relative to two
or more cell sites, a reading from one of the cell sites may be
used in conjunction with other location information, e.g., cell
sector information, to make a location determination.
According to another aspect of the present invention, multiple LFE
inputs, obtained at different times from the same or different
LFEs, are utilized to derive tracking information such as for
obtaining improved location determination accuracy. The associated
method includes the steps of receiving a first LFE input including
first location information and first corresponding time information
for a particular wireless station, receiving a second LFE input
including second location information and second time information
for the wireless station, and using the first and second inputs to
derive tracking information for the wireless station. The tracking
information preferably includes information regarding the mobile
station's speed of travel and direction of travel. This tracking
information can be used in conjunction with subsequent LFE inputs
for the wireless station to improve location determination accuracy
and can also be used to interpolate wireless station location
between location determinations, or to project future wireless
station locations as may be desired for some applications. It will
be appreciated that this tracking function and other functions are
facilitated by the provision of a system for receiving inputs from
one or more LFEs, standardizing such inputs with regard to data
content and format, and storing such information. In particular,
such standardized and stored information can be readily analyzed to
yield derivative information regarding wireless station position as
well as statistical information for wireless stations of interest
in the service area.
A system constructed in accordance with the present invention
includes an input facility for receiving inputs from multiple LFEs,
a memory such as a cache for storing information from the LFE
inputs (e.g., a wireless station identification, a location, a time
associated with that location, an uncertainty for that location,
and travel speed and bearing), an interface for receiving location
requests from wireless location applications and providing
responses to such requests, and a processing subsystem for
processing the LFE inputs and location requests. The apparatus may
also include a facility for prompting LFEs to make location
measurements in response to location requests. Among other things,
the processing subsystem may convert the LFE inputs into a standard
format, direct storage of data in the memory, derive tracking or
other derivative information from multiple inputs, analyzing stored
information relative to received location requests to determine
whether the stored information includes information responsive to
the requests and selectively directing the LFEs to make location
measurements. The system may be resident on a single or multiple
platform and the functionality may be spread among multiple
applications.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and
further advantages thereof, reference is now made to the following
detailed description taken in conjunctions with the drawings in
which:
FIG. 1 is a schematic diagram of a wireless network implementing a
location finding system in accordance with the present
invention;
FIG. 2 is a schematic diagram illustrating a wireless
location-based services system in accordance with the present
invention;
FIGS. 3a-3e illustrate various location finding technologies that
may be utilized in the context of the present invention;
FIG. 4 is a graphical illustration of the use of multiple LFE
inputs to reduce location uncertainty in accordance with the
present invention;
FIG. 5 is a graphical depiction of a location uncertainty analysis
in accordance with the present invention; and
FIGS. 6-9 illustrate various wireless location interface signaling
sequences in accordance with the present invention.
DETAILED DESCRIPTION
In the following description, particular embodiments and
implementations of the present invention are set forth in the
context of a telecommunications network. It will be appreciated
however, that various aspects of the invention are more broadly
applicable to other location based services environments.
Referring to FIG. 1, an wireless telecommunications network
implementing the present invention is generally identified by the
reference numeral 100. Generally, the network includes a mobile
switching center (MSC) 112 for use in routing wireless
communications to or from wireless stations 102, a network platform
114 associated with the MSC 112 for implementing a variety of
subscriber or network service functions, and a variety of location
finding equipment (LFE) systems 104, 106, 108 and 110. In the
illustrated embodiment, the network platform is used to run a
Location Manager (LM) 16 in accordance with the present invention
and a number of wireless location applications 118. Although the
illustrated location finding system 116 and wireless location
applications 118 are illustrated as being resident on the network
platform 114, it will be appreciated that the elements 116 and 118
may be located elsewhere in the network 100, may be resident on
separate platforms, or the functionality of each of these elements
116 and 118 may be spread over multiple platforms. In addition,
other applications not depicted in FIG. 1 may be resident on the
platform 114.
As shown in FIG. 1, multiple LFE systems 104, 106, 108 and 110 may
be associated with the network 100. These LFE systems 104, 106, 108
and 110 may employ any of a variety of location finding
technologies such as AOA, TDOA, GPS and cell/sector technologies
and the various system 104, 106, 108 and 110 may be the same as or
different from one another. It will be appreciated that the nature
of the data obtained from the LFE systems 104, 106, 108 and 110 as
well as the path by which the data is transmitted varies depending
on the type of LFE employed, and the ability to accommodate a
variety of LFEs is an important advantage of the present invention.
Some types of LFEs include LFE equipment in the handset. Examples
include certain GPS and TDOA systems. In such cases, location
information may be encoded into signals transmitted from the
handset to a cell site or other receiver, and the information may
then be transferred to the platform 114 via the MSC 112 or
otherwise. Other LFE systems, i.e., embedded systems use equipment
associated with individual cell sties such as specialized antennae
to make location determinations such as by triangulation and,
again, the resulting location information may be transferred to the
platform 114 via the MSC 112 or otherwise. Still other LFE systems
employ a network of dedicated LFE equipment that is overlayed
relative to the wireless network. Such systems may communicate
location information to the platform 114 independent of the MSC 112
and network cell site equipment. In addition, some LFE technologies
can be implemented via equipment resident in the handset, in cell
sites or other network locations and/or in dedicated LFE sites such
that the data pathway of the location information may vary even for
a given LFE technology.
Three of the illustrated systems 104, 106 and 108 operate separate
from the MSC 112. For example, such systems may include network
based systems AOA and TDOA systems and external systems such as
GPS. Generally, the illustrated network based system such as AOA
and TDOA systems determine the location of a wireless station 102
based on communications between the wireless station and the cell
site equipment of multiple cell sites. For example, and as will be
described in more detail below, such systems may receive
information concerning a directional bearing of the wireless
station 102 or a distance of the wireless station 102 relative to
each of multiple cell sites. Based on such information, the
location of the wireless station 102 can be determined by
triangulation or similar geometric/mathematic techniques. External
systems such as GPS systems, determine the wireless station
location relative to an external system. In the case of GPS
systems, the wireless station 102 is typically provided with a GPS
receiver for determining geographic position relative to the GPS
satellite constellation. This location information is then
transmitted across an air interface to the network 100.
The illustrated cell sector system 110 may be associated with cell
site equipment for communicating with the wireless station 102. In
this regard, the cell site equipment may include three or more
directional antennas for communicating with wireless stations
within subsections of the cell area. These directional antennas can
be used to identify the subsection of a cell where the wireless
station 102 is located. In addition, ranging information obtained
from signal timing information may be obtained to identify a radius
range from the cell site equipment where the wireless station 102
is located, thereby yielding a wireless station location in terms
of a range of angles and a range of radii relative to the cell site
equipment. This cell/sector location information can be transmitted
to the LM 116 via the MSC 112 or possibly via other network
information or structure.
As shown, the LM 116 receives location information from the various
LFE systems 104, 106, 108 and 110. The nature of such information
and handling of such information is described in more detail below.
Generally, however, such information is processed by the LM 116 to
provide location outputs for use by any of various wireless
location applications 118 in response to location requests from the
application 118. Such applications may include any wireless
location services applications such as 911, vehicle tracking and
location-based billing programs.
FIG. 2 illustrates a location-based services system 200 in
accordance with the present invention. An important aspect of the
present invention relates to the operation of the LM 214 to receive
inputs from multiple LFEs 202, 204 and 206 and provide location
outputs to multiple applications 226, 228 and 230. In accordance
with the present invention, the LFEs 202, 204 and 206 may be based
on different technologies, and may therefore provide different
types of location information, in different data formats, with
different accuracies based on different signals.
A number of different location finding technologies are depicted in
FIGS. 3a-3d for purposes of illustration. FIG. 3a generally shows
the coverage area 300 of a cell sector. As noted above, the cell
site equipment for a particular cell of a wireless
telecommunications system may include a number, e.g., three or
more, of directional antennas. Each antenna thus covers an angular
range relative to the cell site bounded by sides 302. In the case
of a three sector cell, each antenna may cover about
120.degree.-150.degree. relative to the cell site. In addition the
coverage range for the antenna defines an outer perimeter 304 of
the coverage area 300. As shown, the range varies with respect to
angle defining a somewhat jagged outer perimeter 304. Accordingly,
the actual uncertainty regarding the location of a wireless station
located in the illustrated cell sector is defined by the coverage
area 300. The location determination output from a cell/sector LFE
is therefore effectively defined by the coordinates of the coverage
area 300.
FIG. 3b depicts a TOA based LFE. In this case, the wireless
station's range from a cell sector antenna is determined, based on
time of signal arrival or signal transit time to within a radius
range, e.g., about 1000 meters. Accordingly, the wireless station's
location can be determined to be within an area bounded by sides
306 (based on the angular range of the cell sector antenna) and
inner 308 and outer 310 arcs (defined by the ranging uncertainty).
The output from a TOA based LFE is effectively defined by the
coordinates of the sides 306 and the axes 308 and 310.
An AOA based LFE is generally illustrated in FIG. 3c. AOA based
LFEs determine the location of a wireless station based on the
angle of arrival of signals, generally indicated by rays 312 and
314, from the wireless station as measured by two or more cell
sites 316 and 318. Each angle measurement has an angular
uncertainty generally indicated by line segments 320 and 322.
Consequently, the uncertainty region for a given location
determination is defined by a polygon having 2n sides, where n is
the number of cell sites 316 and 318 involved in the
measurement.
FIG. 3d illustrates a TDOA based LFE although the illustrated
system is cell site based, the TDOA system may alternatively be
handset based. In TDOA systems, multiple cell sites measure the
time of arrival of signals from a wireless station. Based on such
measurements, each cell site can provide information regarding
wireless station location in terms of a hyperbola 324 or 326 and an
uncertainty, generally indicated by segments 328 and 330. The
resulting uncertainty region is defined by a multi-sided region
(where each wall is curved) having 2n walls, where n is the number
of cell sites involved in the determination.
FIG. 3e illustrates a GPS based LFE. In GPS systems, the wireless
station includes a GPS transceiver for receiving signals indicating
the wireless station's location relative to multiple satellites in
the GPS constellation. Based on these signals, the geographic
coordinates of the wireless station's location is determined to an
accuracy of perhaps 20 meters as generally indicated by circle 332.
This information is then transmitted to the wireless network across
an air interface.
Referring again to FIG. 2, each of the LFEs 202, 204 or 206 outputs
location information to its respective LFC 208, 210 or 212. The
nature of this "raw" LFE output depends in part on the type of LFE
involved. For example, in the case of a cell sector system the
output may be a sector identifier or coordinates; in the case of a
TOA system, the output may be a sector identifier or coordinates
and a radius; in an AOA system the output may be angular
measurements and corresponding cell site identifiers/coordinates;
in TDOA systems the output may define multiple hyperbolae; and in
GPS systems the output may be geographic coordinates.
The LFCs 208, 210 and 212 collect and aggregate the "raw" location
into a standard format which is then sent to the location cache
(LC) 220 of the LM 214 for storage. Aggregation involves using the
raw data to determine a wireless station location and uncertainty.
For some LFE systems, such as GPS systems, this process is simple
because location coordinates are reported and the uncertainty is
known. For other LFE systems, aggregation is more involved. For
example, in the case of TDOA, aggregation may involve receiving
multiple hyperbola definitions and using these definitions to
define a wireless station location and a multi-sided uncertainty
region. The LFCs 208, 210 and 212 may be provided by the LFE
vendors or their functionality may be incorporated into a subsystem
of the LM 214.
In the context of the present invention, it is useful to express
the location information in a standard format. Accordingly, the
LFCs 208, 210 and 212 or a cooperating subsystem of the LM 214
associated with the LC 220, may implement a conversion facility for
converting the determined (processed) location information of the
LFCs 208, 210 and 212 into standardized location information
expressed, for example, as geographical location coordinates and a
region of uncertainty. The uncertainty region may be of any shape
(e.g., polygonal) depending, for example, on the nature of the
LFE(s) employed. Once such type of uncertainty region is a circular
region that can be characterized by an uncertainty radius. In the
illustrated embodiment, two dimensional location coordinates are
defined (e.g., latitude and longitude) together with an uncertainty
radius applied relative to the location coordinates. It will be
appreciated that the standard format may allow for altitude
coordinates, non-circular uncertainty regions and other
parameters.
Referring again to FIGS. 3a-3e, examples of these coordinates and
circular uncertainty regions are graphically depicted. In
particular, in each case, a location "L" and standardized
uncertainty region "C" are geometrically defined such that the
standardized uncertainty region C circumscribes the actual
uncertainty region associated with that location finding
technology. In this regard, the location L may be defined first
(e.g., as the intersection of rays 312 and 314 in FIG. 3c) and then
the minimum radius circle C may be defined to circumscribe the
actual uncertainty region; the standardized uncertainty region C
may be defined first (e.g., as the minimum radius circle required
to circumscribe the actual uncertainty region) and then L be
defined as the center of the circle C; or any other appropriate
geometric solutions/approximations may be employed.
This standardized location information is then stored in a database
in LC 220. Specifically, the location coordinates for a wireless
station and corresponding uncertainties can be stored in a field,
in a relational database, or can otherwise be indexed to a wireless
station identifier, e.g., a cellular telephone Electronic Serial
Number/Mobile Identification Number (ESN/MIN). The coordinates and
uncertainty may be expressed in terms of any appropriate units. For
example, the coordinates may be expressed as latitude and longitude
values in units of 10.sup.-6 degrees and the uncertainty may be
expressed in units of meters.
The stored, standardized information can be used to perform a
number of multiple input analyses. Three examples of such
facilities are generally indicated by the velocity 216, multi-input
processing 217 and tracking 218 facilities of LM 214. The velocity
facility 216 involves determining and storing speed information and
direction (bearing) information for a wireless station based on
multiple LFE inputs for the station. Because of the standardized
format, such determinations can be easily made relative to inputs
from the same or different LFEs 104, 106 and/or 108. The velocity
information can be obtained based on knowledge of the change in
position and the change in time (determined by way of the time
stamps associated with the location information) and may be
expressed in terms of latitudinal and longitudinal velocity
components in units of meters per second, together with velocity
uncertainty terms. The direction information can be directly
obtained from the location information, or can be based on a ratio
of the velocity components, using standard trigonometric
principles. It will be appreciated that such speed and direction
information may be useful for a variety of applications such as
vehicle tracking.
The multi-input processing facility 217 can be used to improve
location accuracy based on multiple inputs from the same or, more
preferably, different LFEs 202, 204 and/or 206. That is, if two
locations with two uncertainties can be obtained for a given
wireless station at a given time, a reduced uncertainty can be
calculated as the overlap of the two original uncertainties. A
complicating factor is that the locations and uncertainties stored
in the LC 220 for a given wireless station will typically not
represent location determinations for the same time. Because
wireless stations are generally mobile, an additional element of
uncertainty is introduced.
The illustrated multi-input processing facility 217 takes time into
account. This is accomplished by:
1. accessing the LC 220 to obtain two (or more) sets of location
information for a given wireless station;
2. identifying a location, uncertainty and time for each set of
information;
3. determining a time difference between the times of the
information sets;
4. calculating an element of location uncertainty associated with
the time difference; and
5. applying the calculated element of location uncertainty to the
earlier location information to obtain time translated location
information. This time translated location information can then be
compared to the later location information in an uncertainty
overlap analysis, as described below, to obtain a reduced
uncertainty.
Various processes can be employed to calculate the additional,
time-related element of location uncertainty. A simple case
involves assuming a maximum rate of travel. For example, a maximum
rate of travel of 70 miles per hour may be assumed to account for
travel of a mobile phone in a vehicle. The uncertainty associated
with an earlier location determination may then be expanded by a
value determined by multiplying the maximum rate of travel by the
time difference between the two measurements to be compared.
Different maximum travel rates may be assumed for different
conditions, for example, a lower rate may be assumed for city
locations than for suburban locations, a lower rate may be assumed
for peak traffic periods, or a lower rate may be assumed for mobile
stations that are not generally used on fast moving vehicles. Also,
wireless station speed and direction information as described above
or other tracking information as described below may be used to
reduce the time-related element of uncertainty.
Once such a time translation process has been employed to normalize
multiple LFE inputs relative to a given time, an uncertainty
overlap analysis can be implemented. Such an analysis is
graphically illustrated in FIGS. 4 and 5. Referring first to FIG.
4, the smaller circle represents a location and uncertainty
associated with a later LFE input taken to be at time t.sub.1. The
larger circle 402 represents a location and uncertainty associated
with a time translated location information based on an earlier LFE
input taken to be at time t.sub.0. Circle 402 is illustrated as
having a larger uncertainty than circle 400 to account for the
additional time and travel related element of uncertainty
associated with the time translation. The shaded overlap area 404
represents the reduced uncertainty achieved by using multiple
inputs. That is, statistically, if circle 400 represents a 95%
confidence level regarding the position of the station at t.sub.1
and circle 402 represents a nearly 95% confidence level regarding
the position of the station at t.sub.1, the position of the station
can be determined to be in the shaded area 404 with a high level of
confidence.
FIG. 5 illustrates a mathematical process for combining the
original uncertainties to obtain a more accurate position and
uncertainty. Mathematically, the problem is to compute the
intersection of the circular uncertainty regions, and express the
result as a location with an uncertainty (e.g., a circular
uncertainty circumscribing the intersection region). To simplify
the mathematics, the geometric arrangement of FIG. 4 is translated
to provide a first axis (x in FIG. 5) that extends through the
centerpoints of the circular uncertainty regions 500 and 502
(generally, the coordinates of the originally determined locations)
and an orthogonal axis (y) intersecting the center of the larger
(in this case later) circular uncertainty region 502. The
mathematical equations for the boundaries of circular uncertainty
regions 500 and 502 are:
It will be appreciated that the values of r.sub.1, r.sub.2 and
x.sub.0 are known as these are the uncertainty of the time
translated information, the uncertainty of the later LFE input and
the difference between r.sub.1 and r.sub.2, respectively. Equations
(1) and (2) can then be simultaneously solved to obtain x and y,
where x is the new location and y is the radius of the new
uncertainty region. Finally, these values can be translated back
into Earth coordinates. This mathematical analysis can be used for
cases where x.ltoreq.x.sub.0 and x.sub.0.ltoreq.r.sub.1 +r.sub.2.
In other cases, the most recent or most accurate of the LFE inputs
can be utilized.
The illustrated LM 214 also includes a tracking facility 218. Such
tracking involves using historical information (at least two sets
of location information) and using such information to reduce the
uncertainty associated with current measurements. That is, by
tracking movement of a wireless station, information can be
obtained that is useful in analyzing the uncertainty of current
measurements. In a simple case, where tracking information
indicates that a wireless station is moving in a straight line (or
otherwise on a definable course) or at a constant speed, then curve
fitting techniques or other simple algorithms can be employed to
obtain a degree of confidence concerning current location.
Moreover, interpolation and extrapolation techniques can be
employed to determine location at times between measurements or in
the future. Such information may be useful to determine when a
wireless station crossed or will cross a boundary as may be
desired, for example, for location-based billing applications or
network management applications (for handling hand-off between
adjacent cells). It will thus be appreciated that the information
stored in the LC 220 may include wireless station identifiers,
locations, uncertainties, confidence levels, travel speeds, travel
directions, times and other parameters. Data may be purged from the
LC upon reaching a certain age in order to remove visitor data and
other unnecessary data.
The velocity facility 216, multi-input processing facility 217, and
tracking facility 218 may use the raw information data transmitted
from the LFEs 202, 204 and 206 to the LFCs 208, 210 and 212 in
place of, or in addition to, the LFC outputs. For example, the
multi-input processing facility 217 may use a hyperbola definition
from a TDOA system in combination with an angle from an AOA system
(or other combination of partial LFE outputs) if such combination
yields an improved location accuracy or otherwise provides a
suitable location determination. Similarly, it may be preferred to
use the raw data for velocity or tracking calculations as such data
is mathematically closer to the moving wireless station and may
more accurately reflect station movement.
Referring again to FIG. 2, the illustrated system 200 includes a
wireless location interface (WLI) 224 that allows wireless location
applications 226, 228 and 230 to selectively access information
stored in the LC 220 or prompt one or more of LFEs 202, 204 and/or
206 to initiate a location determination. The WLI 224 provides a
standard format for submitting location requests to the LM 214 and
receiving responses from the LM 214 independent of the location
finding technology(ies) employed. In this manner, the applications
can make use of the best or most appropriate location information
available originating from any available LFE source without concern
for LFE dependent data formats or compatibility issues. Moreover,
new location finding technologies can be readily incorporated into
the system 200 and used by the applications 226, 228 and 230
without significant accommodations for the existing applications
226, 228 and 230, as long as provision is made for providing data
to the LC 220 in the form described above.
The WLI 224 of the illustrated implementation allows the
applications to include a specification with a location request
regarding the desired location information. For example, the
specification may include one or more of the following: the
timeliness of the location information (e.g., not older than [date
stamp parameter]), the accuracy of the information (e.g.,
uncertainty not exceeding [uncertainty parameters]), confidence
(confidence at least equal to [confidence parameter]).
Alternatively, the request may specify the use of the most recent
available information, most accurate available information, etc. In
addition, the location request can specify whether the request is
for one-time only location information or ongoing monitoring of a
mobile station, whether the LM 214 should wait for the next
available update or force a location determination, whether
redundant or unnecessary updates should be filtered (e.g., do not
send updates more often than once a minute or if wireless station
has moved less than 50 meters), and what the priority of the
request is. In this manner, ongoing monitoring may be employed, for
example, by applications such as vehicle tracking and 911, and
event triggered requests can be used for other applications such as
location based billing. In each case, the desired location
parameters can be specified.
FIGS. 6-9 show messaging sequences for various location request
situations. Specifically, FIG. 6 shows a series of messages for a
location request where the application waits for the next available
location determination. The process is initiated by transmitting a
WLARequestedLocationInvoke message from one of the WLAs to the LC.
This message may include parameter fields for Wireless Station
Identification, WLA Identification, Location Request Filter,
Location Request Mode (check LC or force LFE location
determination), Geographic Extremes (where to look for wireless
station), Request Priority (processing priority relative to other
pending requests) and Fallback Timeout (time that WLA will wait for
a current location determination before accepting the information
stored in the LC).
In the case of FIG. 6, where the WLA waits for the next available
location determination, the next message may be a system access or
other triggering signal from the wireless station to the LFE. In
response, the LFC sends raw location measurement information to the
LFE which, in turn, provides a location update to the LC. The LM
then responds to the location request from the WLA with a
WLARequestLocationReturn Result message. This message may include
the following parameters: Geographic Location, Location
Uncertainty, Location Determination Technology, Time Stamp,
Velocity, Velocity Uncertainty, and Fallback Timeout Occurred
Flag.
FIG. 7 illustrates a sequence of messages associated with a forced
LFE access. The illustrated sequence is initiated by a
WLARequestLocationInvoke as described above. In response, the LM
transmits a QueryLocationInvoke message to the LFC to force an LFE
determination, and the LFC confirms receipt of this message with a
QueryLocationReturnResult message. The parameters of the
QueryLocationInvoke message may include Wireless Station ID,
Geographic Extremes and Measurement Priority (relative to other
pending measurement requests). The LFC then sends a One-time
Measurement Request message to the LFE to instruct the LFE to
obtain location information for the wireless station of interest.
In cases where ongoing monitoring is desired, this message may be
sent repeatedly or periodically as indicated by multiple arrowheads
in the Figure. In order to obtain a location measurement, it is
generally necessary to cause the wireless station to transmit an RF
signal for detection by the LFE or to communicate location data to
the wireless network. This can be achieved by conducting a polling
process using an LRF which requests all wireless stations to
register. In this regard, the LFC issues a Force System Access
message to the LRF which, in turn, transmits the Force System
Access message to the wireless station. In response, a system
access signal is transmitted by the wireless station and detected
by the LFE. The LFE then transmits Location Measurement Information
to the LFC. This may be repeated in the case of ongoing monitoring.
The LFC provides a Location Update to the LC and, finally, the LM
transmits a WLARequestLocationReturnResult as described above to
the WLA.
FIG. 8 represents the case where a location request can be
responded to based on the data stored in the LC. This occurs, for
example, where the cached data satisfies the request specification
or the request specifically seeks data from the LC. Very simply,
the illustrated message sequence involves transmission of a
WLARequestLocationInvoke message from the WLA to the LM and a
responsive WLARequestLocationReturnResult. It will be appreciated
that this case allows for a very fast response. Moreover, it is
anticipated that the cached data will be sufficient in many cases
for many WLAs.
FIG. 9 shows a typical message sequence for the case where a WLA
requests ongoing updates regarding the location of a wireless
station. The update period is initiated upon transmission of a
WLARequestRegisterInvoke message from the WLA to the LM and
receiving a WLARequestRegisterReturnResult in confirmation; and
terminates upon transmission of a WLARequestUnregisterInvoke
message and receiving a WLARequestUnregisterReturnResult in
confirmation. The parameters included in the Register message can
include the wireless station ID, update interval, whether wireless
station access should be forced, etc. As shown in the Figure, the
LM receives Location Updates from time-to-time from the Location
Determination Technology (LDT). It will be noted that only those
Updates occurring between Registration and Unregistration are
communicated to the WLA. In this regard, the Updates are
communicated from the LM to the WLA via a LMLocationUpdateInvoke
message and a LMLocationUpdateReturn Result is transmitted in
confirmation.
The system 200 also includes a Geographic Information System (GIS)
based module 222 for use in correlating geographic coordinate
information to mapping information, e.g., street addresses, service
area grids, city street grids (including one-way or two-way traffic
flow information, speed limit information, etc.) or other mapping
information. For example, it may be desired to convert the
geographic coordinates of a 911 call to a street address for use by
a dispatcher, or to correlate a call placement location to a
wireless network billing zone. In this regard, the GIS module 222
may communicate with the LFCs 208, 210, and 212, the LFC 214 and/or
the WLAs 226, 228 and 230 to correlate location information to GIS
information, and to correlate GIS information to
application-specific information such as wireless network billing
zones. A suitable GIS based module 222 is marketed under the
trademark MAPS by SignalSoft Corporation of Boulder, Colo.
While various embodiments of the present invention have been
described in detail, it is apparent that further modifications and
adaptations of the invention will occur to those skilled in the
art. However, it is to be expressly understood that such
modifications and adaptations are within the spirit and scope of
the present invention.
* * * * *